Synthesis of N-(2-Hydroxyaryl)benzotriazoles via Metal-Free O-Arylation and N–O Bond Cleavage

Abstract

A metal-free method for synthesis of N-(2-hydroxyaryl)benzotriazoles via O-arylation of N-hydroxybenzotriazoles with readily available diaryliodonium salts and sequential N-O bond cleavage under mild conditions has been developed. The [3,3]-rearrangement of N-O bond cleavage could take place on the N instead of C atom. The reaction was compatible with diverse functional groups and a new type of P,N-ligand was synthesized in three steps.

Enantiospecific sp2–sp3 Coupling of ortho‐ and para‐Phenols with Secondary and Tertiary Boronic Esters

“…We postulated that a convenient solution to the poor reactivity of the ortho ‐substituted phenolate would be to incorporate an efficient leaving group on the phenolic oxygen atom prior to boronate complex formation. We selected a benzotriazole (Bt) group as it can be easily introduced, is compatible with organolithium reagents, and is a good leaving group . However, we were also aware that boronate complexes possessing good leaving groups at the ortho ‐position were prone to undergo elimination leading to benzyne formation, which is a potentially competing process.…”

“…ortho ‐Bromophenoxybenzotriazoles 10 a – d were easily prepared in one step by reaction of Ar 2 I + OTf − with hydroxybenzotriazole (HOBt) . Lithium–halogen exchange of 10 a with n BuLi and treatment with boronic ester 6 gave the corresponding boronate complex (see 13 , Table ).…”

The Disappearing Director: The Case of Directed N‐Arylation via a Removable Hydroxyl Group

“…[26] N -(2-Hydroxyaryl)benzotriazoles have been prepared by O -arylation with diaryliodonium triflates, followed by a [33] sigmatropic rearrangement. [27] A summary of these methods is shown in Scheme 1.…”

Enantiospecific sp2–sp3 Coupling of ortho‐ and para‐Phenols with Secondary and Tertiary Boronic Esters

“…We selected a benzotriazole (Bt) group as it can be easily introduced,14 is compatible with organolithium reagents,15 and is a good leaving group 16. However, we were also aware that boronate complexes possessing good leaving groups at the ortho ‐position were prone to undergo elimination leading to benzyne formation,17 which is a potentially competing process.…”

“…ortho ‐Bromophenoxybenzotriazoles 10 a – d were easily prepared in one step by reaction of Ar 2 I + OTf − with hydroxybenzotriazole (HOBt) 14. Lithium–halogen exchange of 10 a with n BuLi and treatment with boronic ester 6 gave the corresponding boronate complex (see 13 , Table 3).…”